A chair includes a seat, a backrest and legs supporting the backrest and the seat. To relieve the user's fatigue and comfortably support the user even during extended periods of sitting, numerous studies have been made on chairs having multi-functions.
As an example of a multifunctional chair, Korean Utility Model Registration Publication No. 20-0355128 discloses a chair with a backrest which is tillable in a backward direction at a predetermined angle.
The prior art multifunctional chair, however, only provides the backward-tiltablity function of the backrest. The prior art multifunctional chair is not adaptable to the change in the user's postures, such as leaning back or standing up of the user sitting on the chair.